Method and apparatus for low-pressure abrasive flow finishing

Abstract

A low-pressure abrasive flow tuning system includes a source of pressurized, Newtonian, low-viscosity flow media. A known-flow path conveys the media to and through a channel of a workpiece to regularize the channel for a predetermined flow rate. The system includes a flow meter that measures flow rate through the known-flow path and workpiece and/or pressure sensors disposed upstream and downstream of the workpiece that measure a drop in pressure through the workpiece. A monitoring and/or controller interface presents indications of the rates and pressures, and permits control of the flow rate through the system.

What is claimed is: 
     
         1 . A method of regularizing a passage in a workpiece using a low-pressure abrasive flow tuning system, the method comprising:
 providing the low-pressure abrasive flow tuning system to provide a low-viscosity abrasive flow medium to at least one internal channel of a workpiece to regularize the flow of the internal channel, the low-pressure abrasive flow tuning system having a known-flow path, the low-viscosity abrasive flow medium having a substantially linear ratio of shear stress to shear rate and including a carrier fluid throughout which an abrasive material is dispersed;   defining at least one of a design pressure drop or flowrate of a low-viscosity abrasive flow medium when passed along the known-flow path and through a calibration orifice related to the desired flow in the internal channel of the workpiece;   fitting a workpiece having the internal channel to the known-flow path;   conveying the low-viscosity abrasive flow medium along the known-flow path and through the internal channel of the attached workpiece;   monitoring a flow rate of the low-viscosity abrasive flow medium through the internal channel of the workpiece using a flow meter disposed upstream of the workpiece and/or monitoring a pressure drop through the workpiece via pressure sensors disposed upstream and downstream from the workpiece; and   stopping the flow of the low-viscosity abrasive flow medium through the internal channel of the workpiece when the flow rate of the low-viscosity abrasive flow medium through the workpiece is substantially the same as the design flow rate of the low-viscosity abrasive flow medium as determined by at least one of design pressure drop or flowrate.   
     
     
         2 . The method according to  claim 1  wherein the defining at least one of a design pressure drop or flowrate is determined by providing a calibration orifice having a cross-sectional area substantially the same as that of an intended flow of the internal channel of the workpiece to the known-flow path and measuring at least one of flow or pressure drop to be established across the workpiece in the low-pressure abrasive flow tuning system to produce a calibrated value. 
     
     
         3 . The method according to  claim 1 , further comprising, prior to fitting the workpiece to the low-pressure abrasive flow tuning system, removing residual manufacturing powder from the workpiece. 
     
     
         4 . The method according to  claim 1 , wherein the viscosity of the low-viscosity abrasive flow medium is between 0 and 2000 cP. 
     
     
         5 . The method according to  claim 1 , further comprising adding plumbing features to the workpiece for attachment to the known-flow path of the low-pressure abrasive flow tuning system. 
     
     
         6 . The method according to  claim 1 , wherein said conveying the low-viscosity abrasive flow medium through the attached flow rate orifice, through the workpiece includes pumping the flow medium through the workpiece only at a pressure less than or equal to 500 psi. 
     
     
         7 . The method according to  claim 1  wherein said low-pressure abrasive flow tuning system includes a reservoir for containing the low-viscosity abrasive flow medium, the tank having an ultrasound transducer, the channel of the workpiece being located to have an output located within the low-viscosity abrasive medium, the ultrasound transducer dislodging abrasive material trapped within uneven surfaces or pits within the internal channel of the workpiece. 
     
     
         8 . The method according to  claim 1 , further comprising:
 performing a chemical etching process on the internal channels in conjunction with the conveying the low-viscosity abrasive flow medium along the known-flow path and through the internal channel of the attached workpiece.   
     
     
         9 . A low-pressure abrasive flow tuning system, comprising:
 a source of pressurized, low-viscosity flow media, the media having a substantially linear ratio of shear stress to shear rate and including a dispersed abrasive material provided in a carrier fluid;   a known-flow path configured to convey the low-viscosity abrasive flow media under pressure from the source to a workpiece, the known-flow path ending in a workpiece holder configured to connect to a channel of a workpiece and to direct the low-viscosity abrasive flow medium into the channel of the workpiece;   one or more sensors disposed along the known-flow path and configured to measure a rate of flow of the low-viscosity flow media and/or a pressure drop of the media within the known-flow path passing through the channel of the workpiece of the low-pressure abrasive flow tuning system;   a controller electrically connected to the one or more of the source of pressurized, low-viscosity abrasive flow media and one or more sensors, the controller determining a rate of flow of the low-viscosity flow media and/or a pressure drop of the media through the channel of the workpiece, the controller comparing the rate of flow to a design flowrate of the low-viscosity abrasive flow media and/or comparing the pressure drop of the low-viscosity abrasive flow media though the channel of the workpiece to a design pressure drop of the low-viscosity abrasive flow media.   
     
     
         10 . The low-pressure abrasive flow tuning system according to  claim 9  where the design pressure drop is ascertained by providing a calibration orifice having a cross-sectional area substantially the same as that of an intended flow of the internal channel of the workpiece to the known-flow path and measuring at least one of flow or pressure drop to be established across a workpiece in a low pressure abrasive flow tuning system to produce a calibrated value. 
     
     
         11 . The low-pressure abrasive flow tuning system according to  claim 9 , wherein the viscosity of the low-viscosity flow medium is between 0 and 2000 cP. 
     
     
         12 . The low-pressure abrasive flow tuning system according to  claim 9 , further comprising an agitator associated with the source of pressurized, low-viscosity flow media, the agitator configured to agitate the low-viscosity abrasive flow medium to maintain or enhance distribution of the abrasive particulate in the flow medium. 
     
     
         13 . The low-pressure abrasive flow tuning system according to  claim 12 , wherein the source of pressurized, low-viscosity flow media is a tank and the agitator includes, disposed in the tank a stirring device, a wiper device, and/or an aerator. 
     
     
         14 . The low-pressure abrasive flow tuning system of  claim 12  wherein the agitator is an ultrasonic transducer, wherein the workpiece is placed within the source with the exit of the channel in said workpiece being submerged within the low-viscosity abrasive medium, the ultrasonic transducer further dislodging loose particulates within uneven surfaces or pits within the internal channel of the workpiece. 
     
     
         15 . The low-pressure abrasive flow tuning system according to  claim 9 , wherein the source of pressurized, low-viscosity flow media is configured to pressurize the flow medium to a pressure only less than or equal to 500 psi. 
     
     
         16 . The low-pressure abrasive flow tuning system according to  claim 1 , wherein
 the one or more sensors include a volumetric flow meter and first and second pressure sensors,   the source of pressurized, low-viscosity abrasive flow media is a pump, and   the controller is configured to receive the measured rate of volume of the low-viscosity flow medium per unit of time from a volumetric flow rate meter, the measured pressure from a first pressure sensor and the measured pressure from the second sensor and is further configured to control at least one of operation and speed of the pump.   
     
     
         17 . The low-pressure abrasive flow tuning system according to  claim 16 , wherein the controller is further configured to automatically adjust the speed of the pump based on one or more of the received rate and pressure measurements. 
     
     
         18 . The low-pressure abrasive flow tuning system according to  claim 14 , wherein the controller is further configured to control the one or more ultrasonic transducers to disturb particles stuck in uneven surfaces of the workpiece. 
     
     
         19 . A non-transient computer readable medium having stored thereon instructions which, when executed by a computer processor electrically connected to a low-pressure abrasive flow tuning system, cause a display associated with the computer processor to present a graphical user interface (GUI) for monitoring and controlling the low-pressure abrasive flow tuning system, the GUI comprising:
 a first pressure field configured to display a first pressure received by the computer processor from a first pressure sensor disposed upstream from a workpiece in the low-pressure abrasive flow tuning system;   a second pressure field configured to display a second pressure received by the computer processor from a second pressure sensor disposed downstream from the workpiece in the low-pressure abrasive flow tuning system;   a flow rate field configured to display a flow rate of a low-viscosity Newtonian abrasive flow medium through the workpiece when the low-viscosity Newtonian abrasive flow medium is conveyed through the low-pressure abrasive flow tuning system, the flow rate received by the computer processor from a flow meter of the low-pressure abrasive flow tuning system; and   a pressure control configured to control a pressure inducing mechanism in the low-pressure abrasive flow tuning system, the pressure inducing mechanism configured to convey the low-viscosity Newtonian abrasive flow medium through the low-pressure abrasive flow tuning system and an internal channel of a workpiece attached to the low-pressure abrasive flow tuning system.   
     
     
         20 . The non-transient computer readable medium according to  claim 19 , wherein the graphical user interface is further configured to display a set point field, the set point field configured to receive from a user or prestored data an entry of a flow rate set point for comparison with the flow rate of the low-viscosity Newtonian abrasive flow medium through the workpiece. 
     
     
         21 . The non-transient computer readable medium according to  claim 20 , wherein the flow rate set point is automatically determined and entered in the set point field as a result of a calibration test, the calibration test measuring a flow rate of a calibration orifice having a cross-sectional area substantially the same as the workpiece.